Many communication systems use Internet Protocol (IP) to transport packet data representative of voice, video, data or control traffic between endpoints (or “hosts” in IP terminology). In such systems, the data is divided into IP packets called datagrams that include addressing information (e.g., source and destination addresses) that enables various routers forming an IP network to route the packets to the specified destination. The destination address may comprise a unicast address identifying a particular host or a multicast address shared by a group of hosts. Typically, the hosts include various fixed devices and mobile wireless devices, often called mobile terminals, that are capable of roaming from site to site or even between different communication networks that use IP.
As wireless communication and mobile internet access have grown in popularity, it is envisioned that multiple IP-addressable devices will be carried within a car, airplane, train (or even on a person). Such a collection of devices is known as a mobile network and the IP-addressable devices residing within the mobile network are known as mobile network nodes. It would be desirable to provide for IP mobility of the mobile network, that is to maintain IP connectivity for the mobile network nodes as the mobile network moves from site to site or between different communication networks.
The most recent IP standard, Internet Protocol version 6, called “IPv6,” supports IP mobility for individual mobile nodes (presently defined in “draft-ietf-mobileip-ipv6-14.txt”) but does not address mobile networks. Generally, mobile IPv6 provides for a mobile node to move to different sites or networks without changing its IP address. A mobile node is always addressable by its “home” IP unicast address associated with a home site or network, regardless of the node's current point of attachment to the network infrastructure. While situated away from its home network, the mobile node is also associated with a unicast forwarding address (known as a “care of” address). The mobile node is addressable either directly by the care of address or indirectly by the home address. In the latter case, the IPv6 protocol causes packets addressed to the home address to be intercepted by a “home agent” and tunneled to the care of address in a manner known as triangular routing.
To that end, mobile IPv6 relies upon a mobile node recognizing when it is at a foreign site and, in such case, to inform its home agent of its new care of address. This is accomplished by a message termed a “binding update.” The mobile terminal may also send binding updates to various devices (termed “correspondent nodes”) prospectively corresponding with the mobile node, such that the correspondent nodes will use the new care of address rather than the home address to avoid triangular routing. Optionally, the binding updates may be “piggybacked” or embedded with other messages sent to the home agent or correspondent node.
A problem that arises (and the main reason why mobile IPv6 does not support mobile networks) is that the mobile network nodes are not necessarily capable of recognizing when they are at a foreign site or new access technology, such that they would be able obtain respective care of addresses and send binding updates. Indeed, it is preferred that most mobile network nodes, while attached to the mobile network, need not be aware of the movement of the mobile network from site to site or to new access technologies. Moreover, even if they were, it is preferred that most mobile network nodes will not send binding updates so as to prevent so called binding update “storms” that could result from multiple mobile network nodes simultaneously sending binding update messages through the network. As will be appreciated, binding update storms create network traffic overhead that can adversely affect handoff times and quality of service of the network.
A related problem is that binding updates contain implied geographic location information that enable a recipient of the binding update to determine the location of a mobile network node. It would be desirable for certain mobile network nodes (i.e., those that do not wish to broadcast their new location throughout the network), to establish privacy attributes that would specify to whom binding updates should be sent through the network on their behalf. In such manner, the mobile network node could keep its location secret from some, or all correspondent nodes based on the privacy attributes. Advantageously, the privacy attributes may be selected independently by individual mobile network nodes.
Accordingly, a need has arisen to provide IP mobility support for mobile networks in a manner that builds upon the capabilities of mobile-IPv6, yet reduces or eliminates the number of binding updates that are required upon movements of the mobile network from site to site or between dissimilar access technologies. Advantageously, the IP mobility solution will allow for mobile network nodes to specify how binding updates should be sent on their behalf as the mobile network moves from site to site. The present invention is directed to satisfying these needs.